Raid 5; Raid 6 - American Megatrends StorTrends 2200 User Manual

RAID 5

RAID 5 includes disk striping at the byte level and parity. In RAID 5, the parity
information is written to several hard disk drives. RAID 5 is best suited for networks that
perform a lot of small I/O transactions simultaneously.
RAID 5 addresses the bottleneck issue for random I/O operations. Since each hard disk
drive contains both data and parity numerous writes can take place concurrently. In
addition, robust caching algorithms and hardware based exclusive-or assist make RAID 5
performance exceptional in many different environments.
Point Description
uses RAID 5 provides high data throughput, especially for large files. Use RAID 5 for transaction
processing applications because each hard disk drive can read and write independently. If a hard
disk drive fails, the StorTrends iTX Software uses the parity stored on each of the other hard disk
drives to recreate all missing information. Use also for office automation and online customer
service that requires fault tolerance. Use for any application that has high read request rates but
low write request rates.
strong points Provides data redundancy and good performance in most environments
weak points Hard disk drive performance will be reduced if a hard disk drive is being rebuilt. Environments
with few processes do not perform as well because the RAID overhead is not offset by the
performance gains in handling simultaneous processes.
hard disk drives Three to 32 hard disk drives

RAID 6

RAID 6 uses distributed parity, with two independent parity blocks per stripe, and disk
striping. A RAID 6 virtual disk can survive the loss of two disks without losing data.
RAID 6 is similar to RAID 5 (disk striping and parity), except that instead of one parity
block per stripe, there are two. With two independent parity blocks, RAID 6 can survive
the loss of two disks in a virtual disk without losing data.
Point Description
uses Provides a high-level of data protection through the use of a second parity block in each stripe.
Use RAID 6 for data that requires a high-level of protection from loss.
In the case of a failure of one drive or two drives in a virtual disk, the RAID controller uses the
parity blocks to recreate the missing information. If two drives in a RAID 6 virtual disk fail, two
drive rebuilds are required, one for each drive. These rebuilds do not occur at the same time. The
controller rebuilds one failed drive at a time.
Use for office automation and online customer service that requires fault tolerance. Use for any
application that has high read request rates but low write request rates.
strong points Provides data redundancy, high read rates, and good performance in most environments. Can
survive the loss of two drives or the loss of a drive while another drive is being rebuilt. Provides
the highest level of protection against drive failures of all of the RAID levels. Read performance
is similar to that of RAID 5.
weak points Not well suited to tasks requiring lot of writes. A RAID 6 virtual disk has to generate two sets of
parity data for each write operation, which results in a significant decrease in performance
during writes. Disk drive performance is reduced during a drive rebuild. Environments with few
processes do not perform as well because the RAID overhead is not offset by the performance
gains in handling simultaneous processes. RAID 6 costs more because of the extra capacity
required by using two parity blocks per stripe.
hard disk drives Three to 32 hard disk drives
162 StorTrends/ManageTrends (version 2.7) Web Interface User's Guide for the StorTrends 2200 Storage Appliance